Alkanes are an abundant but chemically intractable class of compounds that offer the potential of inexpensive substrates for conversion to functionalized chemical products, provided that economical processes can be developed to convert the alkanes to substances containing functional groups such as alcohols, amines, acyls, olefins, halocarbons, organosulfur compounds and organotin compounds.
Natural gas (NG) is becoming an increasingly abundant resource in the US and around the world. While NG is used for heating it would be ideal to upgrade this resource to chemicals and liquid fuels. This could augment or potentially replace petroleum as the feedstock for chemicals and fuels. Natural gas is also abundantly available in remote locations where transportation to centers of use is not economically viable. In these cases it would be desirable to have an inexpensive process to convert the natural gas to a more easily transported form such as a liquid. However, the existing high-temperature, indirect processes based on the conversion of natural gas to syngas (CO/H2) followed by conversion of the syngas to chemicals and liquid fuels are too energy and capital intensive to economically compete with products from petroleum. Current processes for the conversion of natural gas to fuels and chemicals require high-temperature (>800° C.) to generate synthesis gas or olefins. FIG. 1(A), below, illustrates some of these reactions of alkanes. These processes are very capital and energy intensive and are only economical at very large scales. It is generally considered that a direct, lower temperature (<300° C.), selective process to convert the gases in NG (primarily methane, ethane and propane) to liquid products such as alcohols could be used to generate chemicals and liquid fuels at much lower cost than the existing high-temperature, indirect syngas processes.
A technology for the direct low-cost conversion of the major components of natural gas (methane, ethane, propane) to liquid fuels and chemicals such as oxygenates would provide a path to increased value for these sources of natural gas. The potential market for such technology is large; e.g, the global market value for ethylene glycol is over $20 billion/yr with the US at over $4 billion/yr. The markets for other oxygenates such as methanol, ethanol (that can also be inexpensively converted to ethylene and polyethylene), isopropanol, propylene glycol, etc., are also very large. The liquid fuels market is enormous; a 2% penetration of the projected US transportation fuels market, equivalent to the projected annual growth rate in the US, would represent about 50 plants of 14,500 barrel per day capacity.
Other hydrocarbon sources are available for which it may also be desirable to carry out one or more of the functionalization reactions described herein. For example, crude or refined petroleum products, tar sand extracts and distillates, coal and coal liquification products, and other materials containing alkane-like moieties, can be substrates for the reactions described herein, for the production of valuable industrial chemicals.